http://en.wikipedia.org/wiki/Two-port_network 

http://www.ee.hacettepe.edu.tr/~solen/Matlab/MatLab/Matlab%20-%20Electronics%20using%20MatLab%20-%20chapter%2007%20-%20Two-Port%20Networks.pdf

http://fourier.eng.hmc.edu/e84/lectures/ch2/node4.html

http://web.cecs.pdx.edu/~ece2xx/ECE222/Slides/TwoPortsx4.pdf

http://www.google.com/url?sa=t&rct=j&q=Two+Port+Network&source=web&cd=7&ved=0CGEQFjAG&url=http%3A%2F%2Fweb.utk.edu%2F~green%2Fnotes%2FTwo%2520port%2520networks.ppt&ei=uS7PT7DhLYOl-gbaqL2LDA&usg=AFQjCNF1bQQDH1VbO_5qWZfGTcpu5bJmNw

http://en.wikibooks.org/wiki/Circuit_Theory/Two_Port_Networks

http://ctmd.oum.edu.my/v2/tutorkits/EBEC3103%20Circuit%20Theory/EBEC3103%20(Topic%209)%20Circuit%20Theory.ppt

http://jcatsc.com/media/ee541/LectureAids/01-F10_TwoPorts.pdf

http://books.google.com/books/about/3000_Solved_Problems_in_Electric_Circuit.html?id=HhgbUDGaJ30C

http://engr.case.edu/merat_francis/eecs397/Two-port%20Networks.pdf

http://my.safaribooksonline.com/book/electrical-engineering/9780470633229/chapter-16-two-port-networks/problems0043#X2ludGVybmFsX0ZsYXNoUmVhZGVyP3htbGlkPTk3ODA0NzA2MzMyMjkvODE2

http://www.google.com/url?sa=t&rct=j&q=%D8%B4%D8%A8%DA%A9%D9%87+%D8%B3%D9%88%D8%AF%D9%87+%D8%AF%D8%B1+%D9%85%D8%AF%D8%A7%D8%B1%D9%87%D8%A7%DB%8C+%D8%A7%D9%84%DA%A9%D8%AA%D8%B1%DB%8C%DA%A9%DB%8C&source=web&cd=1&ved=0CEsQFjAA&url=http%3A%2F%2Fwww.pnu.ac.ir%2Fportal%2FFile%2FShowFile.aspx%3FID%3D244a4f98-11fe-418d-9a07-b795600d6cd2&ei=FYbUT9GfBM6S0QX2tZH_Aw&usg=AFQjCNEmT84o_rk05bW0GAGjLyIxl9gtPQ